#define _CRT_SECURE_NO_WARNINGS
class Solution {
public:
    bool isUnique(string astr) {
        if (astr.empty())
            return true;
        sort(astr.begin(), astr.end());
        for (int i = 0; i < astr.size() - 1; i++)
        {
            if (astr[i] == astr[i + 1])
                return false;
        }
        return true;
    }
};